Reciprocating internal combustion engines generally comprise, among other things, a crankshaft for power output. Engine accessory components are driven by a belt connected to a pulley on one end of the crankshaft. During operation the crankshaft vibrates in various modes due to the reciprocating nature of the engine. Such vibration can adversely affect operation and long-term reliability. Consequently, viscoelastic dampers may be incorporated into crankshaft pulleys to damp crankshaft vibration. Such combinations of pulley and viscoelastic damper are simply referred to as “crankshaft dampers”. The crankshaft damper generally comprises an inner hub and an outer pulley. The outer pulley is generally attached to the inner hub by a viscoelastic elastomeric ring.
In certain applications crankshaft dampers may include a pulse ring or timing gear for engine ignition timing. The pulse ring rotates in front of a sensor attached to the engine. The pulse ring generally includes a gap as a reference point, for example, to indicate TDC for cylinder one. The pulse ring is generally attached to the crankshaft damper outer pulley. However, due to the vibration and relative motion, albeit small, of the hub to the pulley made possible by the elastomer ring, accurately detecting the pulse ring location on the outer pulley can be adversely affected. Consequently, for very precise applications, the pulse ring is attached to the inner hub, which is then rigidly assembled on the crankshaft. However, prior art pulse rings comprise a separate part that must be press fit, welded or otherwise attached using other means to the inner hub.
Representative of the art is U.S. Pat. No. 5,203,223 (1993) to Himmeroeder that discloses a cold-former gear made from a single circular sheet of sheet metal.
Also representative of the art is U.S. Pat. No. 5,966,996 (1999) to Hamaekers that discloses an annular machine part comprising at least two metal machine elements which are separated from each other by a viscoelastic layer. A separately produced extension piece projects from one of the machine elements.
Also representative of the art is a crankshaft damper manufactured by Freudenberg NOK having an inner hub and an outer ring joined by an elastomeric ring. A pulse ring is press fit into the inner hub.
The prior art pulse rings are not integral to the inner hub making them subject to detaching from the inner hub or damper.
What is needed is a crankshaft damper having an integral pulse ring. What is needed is a crankshaft damper having an integral pulse ring whereby the integral pulse ring is flow formed on an inner hub. The present invention meets these needs.